Protective system



March 28, 1944. v A. PALME ETAL 2,345,420

PROTECTIVE SYSTEM Filed Jan. 3, 1942 T0 LOAD Arthur Palme, Casimere A. urbanek,

y Their Attorney.

Patented Mar. 28, 1944 UNITED STATES PATENT OFFICE PROTECTIVE SYSTEM Arthur Palme, Pittsfield,

and Casimere A.

Urbanek, Adams, Mass, assignors to General Electric Company, a corporation of. New York 3 Claims.

This invention relates to protective systems and more particularly to a new and improved electrical interlocking system for a pair of movable devices.

Occasionally it is necessary to provide an interlock between a primary movable device and a secondary movable device so that the latter can only be moved when the former is in its safety or normal position and so that the latter cannot be moved away from its safety or normal position until the former is returned to its normal position. For example, where an arcing duty switch, such as an oil circuit breaker, is connected in series with a non-arcing duty switch, such as a tap-changing switch for a transformer, of the type which is not adapted to operate under load, it is necessary to open the arcing duty switch before the non-arcing duty switch can be opened and similarly it is necessary to insure that the non-arcing duty switch has been returned to its fully closed position before the arcing duty switch is reclosed.

In accordance with the present invention there is provided a novel and simple electrical interlocking system between devices of this kind so as positively to prevent hazardous operation of the secondary device.

An object of the invention is to provide a new and improved electrical interlocking system.

Another object of the invention is to provide a practically fool-proof electrical interlocking system between primary and secondary movable devices.

The invention will be better understood from the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

Referring now to the drawing, which diagrammatically illustrates a preferred embodiment of the invention, there is shown therein a main alternating-current power circuit I in which is connected a power transformer 2. For controlling the energization and de-energization of the transformer 2 there is provided a normally closed arcing duty switch, such as an oil circuit breaker 3, connected in the circuit I between its source end and the transformer. For varying the ratio of the transformer there is provided a normally closed dial-type ratio switch 4 having a movable contact 5 for selectively making bridging connection between adjacent fixed contacts which are selectively connected to taps in the secondary winding of the transformer. This dial switch is operated by a hand wheel 6 and is relatively slow moving and therefore not suitable for arcing duty such as would be imposed upon it if it were attempted to operate it when the transformer 2 was energized.

The non-arcing duty switch 4 is held in its fully closed position by means of a gravity-operated bolt-type lock or latch shown as a movable plunger I which fits into the slot in a circular member 8 mounted concentrically on the shaft of the hand wheel 6. The operating means for the switch 4 is shown schematically and it is to be understood that wheel 6 and member 8 make one complete revolution for each complete tap change produced by the switch 4.

The arcing duty switch 3 is arranged to be opened at any time by means of a conventional tripping coil 9 controlled by an opening push button switch ID. The lock or latch for the switch 4 is withdrawn or released by means of an electroresponsive device, such as a solenoid winding II whose energization is controlled by means of a set of normally open back contacts I2 on the switch 3. These back contacts close when the main contacts of the switch 3 open. As shown, the circuit including the winding II and the back contacts I2 may be energized by any suitable source of current supply. Consequently, whenever the arcing duty circuit breaker 3 is in its open position the bolt 7 is raised or withdrawn so that the non-arcing duty switch A may be operated.

For closing the arcing duty switch 3 there is provided suitable electroresponsive means shown schematically as a coil 13, the energization of which is controlled by a set of normally open main control contacts [4 on a closing push button switch I5. However, in order to prevent energization of the closing means for the switch 3 in case the non-arcing duty switch 4 is not fully closed there is provided a second interlock in the form of a set of normally closed contacts (6 which are arranged to be opened when the bolt 1 is raised or withdrawn.

By means of the slotted circular member 8 it is impossible for the second interlock contacts IE to be closed accidentally at any time when the switch 4 is not fully closed so that, for example, a failure of current to the winding I I cannot cause the contacts I6 to close unless the switch 4 is fully closed.

It will thus be seen that there is a first interlock consisting of the winding II and the back contacts l2 for preventing opening of the switch 4 until after the switch 3 has been opened and there is a second interlock consisting of the contacts I6 for preventing the switch 3 from being push button l4 will first de-energize the winding- II by reason of the opening of the control contacts il. However, as previously explained, the bolt cannot drop into its locking position unless the switch 4 has been fully; closed and therefore the second interlock contacts l6 cannot" close until the switch 5 is fully closed. However, if

that is the case, then the closing of the normally open contacts I4 will complete a circuit for the closing, means i3 through, thesecond interlock contacts [6,.

This interlocking system is positive and substantially fool-proof because the locking. of the switch 4 is done by gravity and the switch 4, will stay locked if the winding H shouldburn. out or if the plunger 1. should. stick or if the control power should fail. Also,v as has. previously been explained, once the plunger 1 has been withdrawn and' the switchl i has. been moved off. of its fully closed position the second interlock contacts l6. are mechanically held open independently of the electromagnetic action of the raising winding, II so that it is impossible to reclose the main arcing duty switch 3 until the non-arcing duty switch 4has been fully reclosed.

While there has been shown and described a particular embodiment of this invention, it will be obvious to those skilledin the art that various changes and modifications can be made therein without departing'from the invention and, therefore, it is aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What we claim as new and desire to secure'by Letters Patent of the United States is:

1'. In combination, a primary movable device having a normalposition and an abno-rmalposition, a secondary manually movable device having a normal position and an abnormal position, an electrically operated mechanical interlock controlled by said primary device for preventing movement of said secondary device away from its normal position when said primary device is in its normal position and having an actuated position for permitting movement of said secondary device away from its normal position when said primary device is inits; abnormal position, an electrical interlock controlled jointly by said electrically operated mechanical interlock and by saidse'condary device for preventingsaidiprimary device'lfrom: being returned from its'abnorm'al position to its normal position when saidsecondary device isin its abnormaliposition andwhensaid electrically operated mechanical interlock'isin its actuatedposition, electroresponsive means for re. turning said primary device from its: abnormal position to its normal position, a master controller for controlling said means coincidentally with said electrical interlock, and means operated by said master controller for deactuating said electrically operated mechanical interlock whereby if said secondary device has been returned to its normal position said electrical interlock will permit said master controller to operate said electroresponsive means so as to return said primary device from its abnormal position to its normal position.

2. An electrical interlocking system comprising, incombination, an electric power supply system, an arcing duty switch and a manually-operated non-arcing duty switch effectively serially connected in said supply system, means for opening said arcing duty switch at any time, a gravity operated latch forholding said non-arcing duty switch in its fully closed position, electroresponsive means for releasing said latch so as to permit opening of said. non-arcing duty. switch, a set ofnormally open auxiliary contactswhich are closed by the openingoof said arcing duty switch, a source of current connected to energize said electroresponsive means throughv said auxiliary contacts, a second electroresponsive means for closing, said arcingduty switch, a set of normally closed contacts on said latch which are opened when said latch is rel'eased, a manually operated control switch for controlling the energization of said second electroresponsive means through said set of' normally closed contacts,. and a set of normally closed back contactson saidcontrol switch connected in series with said auxiliary contacts.

3: In combination, an arcing duty switch, a manually-operated non-arcing duty'switch effectively connected in series therewith in a com:- mon electric power supply system, means for opening said arcing duty-switch at anytime, electroresponsive means for closing said arcing duty switch, atwo-position control switch having a set of normally open control contacts and a set of normally closed control contacts, said set of'nor mally open contacts being connected in series with a source of current supply for controlling the energ-ization of said electroresponsive means, a gravity-operatedbolt=type-1ock for holding said non-arcing duty switch in its fully closed position, a second electroresponsi've means for raising said bolt-so as to permit opening of saidnonarcing duty switch, mechanical means for-locking said bolt in its raised position whenever said non-arcing: duty switch is in other than its fully closed position, a set of normally closed interlock contacts. arranged to be opened whenever said boltxisraised, said=normally closed interlock contacts being connected in series withsaid normally open control contacts, a set ofnormally open backicontacts onsaid arcing duty'switch arranged to beeclosedi whenever said arcing duty switch is opened; and a series circuit including said normally closedcontrol contacts, said normally open back contacts, said second' electroresponsive device. andia source of current'suppl'y.

ARTHUR PALME; CASIMERE A. URBANE-K. 

